Treatment of alunite and the like.



attie.

ED sir oration.

,cHARLEs H. MAcDOVVELL, OF CHICAGO, inrrlvo s, AssieNoR TO THE MINERAL PRODUCTS COMPANY, OF NEW YORK, N. Y., A- CORPORATION OF WEST VIRGINIA.

TREATMENT OF ALUNITE AND THE LIKE.

NO Drawing.

To all tvhomit may concern Be it known thatI, CHARLES H.

DownLL, a citizen of the United States, re-

siding at Chicago, county of Cook, State of Specification of Letters Patent.

Patented A i so, 1915.

Application filedJuly 31, 1914:. Serial No. 854.278.

' ture as 1600 C. leaving traces only (say not ,the calcined alunite treated. It is also found As a typical example of the material suitable for the practice of the invention, it may be assumed, for instance, that the alunite employed may have a general formula saysubstantially as follows, to wit: A1 0 37.18; Fe O trace; SO 38.3%; P 0 .58; K 0, 10.46; Na,O, .33; H O+, 12.90; H,,O,

stood, that this analysis is merely typical of other and like analyses of alunite, and that it is given for the purpose of indicating generally the character of the raw material which has been found particularly serviceable in practice.

In carrying out the invention, the procedure is as follows: The alunite or like material referred to is calcined under the conditions, specified, for instance, in U. S. patent issued to Howard F. Chappell, No. 1,070,324 under date of August 12, 1913, and at a temperature suflicient to drive off the sulfur combined with the alumina in the form of sulfurous anhydrid and sulfuric anhydrid. The product of this calcining more than about .5% of K 0 and Na.,()) in that the volatilized potassium and sodium salts-may be recovered as such in solid form by conveying them into a cooling flue Or re ceptacle wherein, as the'temperature drops below the temperature of volatilization, they will be deposited, and from which they may be collected in condition suitable for utiliza- -t1on, storage, or shipment, as dry products.

This capacity of the process, 71. 6., to yield,

as a direct product of theoperation, the volatllized and subsequently deposited salts indry form, avoids the expense and incon- 'venience -attendant upon their recovery by 109; SiO .22. It will, ofcourse,'be underleaching, and is of further industrial importance in those locatities where suflicient quantities of water are either unavailable or are diflicult of procuring... So also, the volatilization of the salts, according to the present invention, may immediately succeed the preliminary-calcining operation, so that, in such instance, it will merely be necessary to add the requisite additional units of heat I to eifect the desired result;,thereby substioperation consists of alumina insoluble 1n alkali, and of potash (potassium sulfate) soluble in water, together with a minor portion of water-soluble sodium sulfate. The temperatures of the ,sulfurous anhydrid and sulfuric required for the driving off anhydrid, in the calcining operation referred calcined tuting a furnace operation for'the combined furnace operation and leaching operation of the former practice. Where water is freely available, or where it is desired, for any special reason, to recover the volatilized salts in the form of a solution, they may be brought intocontact with water, as, for instance, by spraying them with water in the collecting flue or chamber, or otherwise. In general, however, it ,will be preferable. to recover them in the dry state, as hereinbefore indicated. The calcined alunite to be treated for the volatilization of its potassium and sodium salts may be heated, to the desired temperature, inany suitable manner,

(as, fpr instance, either by external or internal heating, electrical, or otherwise), and either in a neutral atmosphere, a reducing atmosphere, or an oxidizing atmosphere.

My invention involves the further discovery that if the calcined alunite, 1 in a finely divided condition, is v admixed with from 20% to 50% .of carbon (preferably in the carbon serves mechanically to assist in the disengagement of the volatilized salts. In order to make available to the best degree the useful functions due to' the presence of carbon in the charge, a sufficient surplus of carbon should be provided if air or any other carbon-consuming agent is introduced into the rotary kiln or other furnace in which the charge is being treated, so as to practically maintain the percentage of carbon in the charge at from 20% to over the amount consumed by the introduced carbon-consuming agent, It will be found convenient, in some instances, to start with the introduction of the carbon into the raw alunite charged into the calcining kiln, so that the carbon may be present and in a highly heated condition in the charge when, upon raising the temperature, the volatilization of the salts begins. This introduction of carbon into the initial charge of raw alunite has the further advantage of avoiding the additional expense and inconvenience of separately admixing the carbon with the charge after calcination of the raw alunite. The passage of a current of nitrogen, a current of air, 'a current of products of combustion, or the like, through the charge has thefurther useful effect of assisting in carry= ing off the volatilized salts.

I While the practice of the invention is not restricted to the use of any particular apparatus, it will be found convenient to employ the usual inclined rotary kiln.

In so far as I am aware, the discovery that, by the application of heat to calcined alunite, the potash and sodium salts contained therein, can be volatilized and driven off as such is broadly new and fundamental, and could not have been predicted by those skilled in the art. On the contrary, in view of the fact that sodium aluminate is manufactured by heating bauxite, or some other form of alumina, with carbon and sodium sulfate, the logical inference would have been that a mixture of carbon with calcined alunite containing potassiuin sulfate, would, I

like, which comprises first calcining lll16 alunite for the purpose of driving off sulfurous anhydrid and sulfuric anhydrid, and then heating it to a higher temperature to volatilize and drive off potash.

2. The method of treating alunite and the like, which comprises first calcining the alunite for the purpose of driving off sulfurous anhydrid and sulfuric anhydrid, and

then heating it to a higher temperature, in Y the: presence of carbon, to volatilize and drive off pot-ash.

3. The method of treating alunite and the like, which comprises first calcining the alunite for the purpose of driving off sulfurous anhydrid and sulfuric anhydrid, then heating it to a highertemperature sufficient to volatilize and drive ofi potash, and depositing the volatilized potash as a solid.

4. The method of treating alunite and the like, which comprises calcining the alunite for the purpose of driving off sulfurous anhydrid and sulfuric anhydrid, then heating it to a temperature sufficient to volatilize and drive off potash, and expediting the exit of the volatilized potash from the charge by carrying it ofi in a' gaseous current In testimony whereof I affix my slgnature,

in presence of twolwitnesses.

CHARLES H. MAcDOWELL. Witnesses G. F. HAcEnoRE, F. S. LODGE. 

